---
title: "DS properties and interaction model"
subject: "Distributed System"
chapter: 1
key: "semester_7/distributed_system:ds-properties-interaction-model"
source: https://www.bctengineer.com/q/semester_7/distributed_system/ds-properties-interaction-model
site: BCT Engineering
---

# DS properties and interaction model

Distributed System · Chapter 1: Introduction

- Asked in: 2071 Shrawan, 6+2 marks
- Video: [Fundamental Models | Distributed Systems | Lec-10 | Bhanu Priya](https://www.youtube.com/watch?v=dQ5OhyAwXVg) — Education 4u
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/distributed_system/ds-properties-interaction-model
- Whole chapter: https://www.bctengineer.com/md/semester_7/distributed_system/chapter-1

## Question

Discuss the properties of Distributed System (DS). How does the interaction model address the relevant issues in DS?

## Short answer

Properties include concurrency, no global clock, independent failures, heterogeneity, openness, scalability, transparency, resource sharing, and message passing. The interaction model characterizes communication latency, bandwidth, jitter, clock drift, and synchronous versus asynchronous timing, and uses logical clocks for event ordering when no global time exists.

## Answer

#### Properties of a distributed system
- **Concurrency:** components execute in parallel and share resources.
- **No global clock:** coordination is only by message passing; each computer has its own clock, with drift.
- **Independent (partial) failures:** a component or link may fail while others continue.
- **Heterogeneity:** variation in hardware, OS, network and languages.
- **Openness, scalability and transparency.**
- **Resource sharing** and **message-passing communication** with delays.

#### Interaction model
Processes in a distributed system interact by passing messages, and the performance of communication limits what can be done. The interaction model addresses the following issues.

1. **Performance of communication channels:** characterised by *latency* (delay between sending and receipt), *bandwidth* (amount of data per unit time) and *jitter* (variation in delivery time of messages, vital for multimedia).
2. **Computer clocks and timing events:** each process has its own clock, and clocks drift at different rates (*clock drift rate*). Two processes cannot give exactly matching timestamps.
3. **Two variants of the model**
   - **Synchronous:** known upper bound on process execution time, message delay and clock drift. Timeouts can be used to detect failure, but real systems seldom guarantee this.
   - **Asynchronous:** no bounds; a slow process cannot be told from a failed one. It reflects the Internet and is the safer general assumption.
4. **Event ordering:** because there is no global time, the order of events is found using logical clocks (Lamport, "happened-before") instead of physical time.

So the interaction model states the assumptions about delay, clock and ordering, and thereby decides which algorithms (such as failure detection or mutual exclusion) are possible.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which is a property of a distributed system?
   A. No global clock, with each computer having its own drifting clock
   B. A single shared clock
   C. Shared memory between all nodes
   D. Failures always affect all components together
   Answer: A. Coordination is by message passing and clocks drift independently. (Key point: Properties)

2. What is jitter in communication channel performance?
   A. The amount of data per unit time
   B. Variation in the delivery time of messages
   C. The delay between send and receipt
   D. The number of processes
   Answer: B. Latency is delay, bandwidth is data rate, jitter is variation in delivery time (vital for multimedia). (Key point: Jitter)

3. Why is the asynchronous model considered safer for the Internet?
   A. Message delay is always bounded
   B. Clock drift is zero
   C. There are no time bounds, and a slow process cannot be told from a failed one
   D. Timeouts reliably detect failure
   Answer: C. The Internet gives no guarantees on delay, so asynchronous assumptions are safer. (Key point: Asynchronous model)

4. How is the order of events determined without global time?
   A. Using physical timestamps from each machine
   B. Using bandwidth measurements
   C. Using the machine's IP address
   D. Using logical clocks (Lamport's happened-before)
   Answer: D. Physical clocks cannot match exactly, so logical clocks order events. (Key point: Event ordering)

## Related in Distributed System

- [Centralized vs distributed; design issues](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Acentralized-vs-distributed) — Distributed System, chapter 1
- [Transparency properties of DS](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Ads-transparency-types) — Distributed System, chapter 1
- [DS as a single coherent system](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Asingle-coherent-system) — Distributed System, chapter 1, asked 2×
- [Ricart-Agrawala performance issues](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Ara-performance-alternate) — Distributed System, chapter 6
- [Autonomous vs distributed system](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Aautonomous-vs-distributed) — Distributed System, chapter 1
- [Models of distributed system](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Amodels-of-ds) — Distributed System, chapter 1

## Related in other subjects

- [Issues modern configuration management must address](https://www.bctengineer.com/question.md?key=semester_5%2Fsoftware_engineering%3Asurvival-of-fittest) — Software Engineering, chapter 10
- [Short note: Distributed system implementation](https://www.bctengineer.com/question.md?key=semester_6%2Fobject_oriented_analysis_and_design%3Ashort-note-distributed-implementation-issues) — Object Oriented Analysis and Design, chapter 4
- [Distributed system in big data example](https://www.bctengineer.com/question.md?key=semester_8%2Fbig_data_technologies%3Adistributed-system-example) — Big Data Technologies, chapter 1
- [Distributed system and Hadoop](https://www.bctengineer.com/question.md?key=semester_8%2Finformation_system%3Adistributed-system-hadoop-voluminous-data) — Information System, chapter 8